With now less than a week until the start of spring training, baseball's free-agent market stands frozen at an unprecedented level. Just over half of this winter's free agents remain unemployed, including 11 of Keith Law's top-20-ranked free agents.

Though various underlying explanations combined to create this state, these players will inevitably sign with teams at some point. This means teams still have the opportunity to upgrade their rosters more than is usually possible in February.

The question becomes: Which teams have the most incentive to bring in the remaining free agents, especially the difference-makers? This has been a quiet year -- for signings, at least -- for teams such as the New York Yankees and Los Angeles Dodgers at the top of the scale, trying to stay below the luxury tax that functions as a soft salary cap. And by and large, the rebuilding teams would rather keep their powder dry and not chase after this year's most coveted available players. That just leaves baseball's middle class, the teams that still seek to join the elites for the 2018 season rather than the penurious.

For the purposes of defining the middle class of 2018, I'm using teams that currently project with a ZiPS probability between 33.3 percent and 66.6 percent as the teams with their 2018 fates most up in the air.